Transmission of fressure in porous media under explosive loading

Abstract

A large number of schemes exists for explosive loading of materials but the most widespread is apparently the scheme represented in Fig. la. It is seen that the detonator front of the explosive substance (ES) is oriented perpendicularly to the explosive substance-loading material interface. Such a situation is realized when a layer of explosive whose constitution is identical over the whole volume is placed in contact with the material and initiation occurs at some arbitrary point of the charge. In practice such a loading is applied in thrusting plates in explosive welding, explosive hardening, dynamic compaction of porous bodies, etc. The action of the detonation products (DP) on the substance under such loading can apparently be considered studied sufficiently so that such a scheme can be applied in practice [1-5]. It is interesting to examine the more general case when the detonation front is not perpendicular to the explosive-loaded substance interface but is inclined at a certain angle to the normal (Fig~ Ib and c). It must be noted that in the stationary sliding detonation mode the pattern shown in Figs. ib and c can be obtained only by a special method using a two-layer charge. The situation with ~ 0 (see Fig. ib) when the explosive with higher detonation rate is between the main charge and the medium. To simplify the problem we consider the high velocity charge layer to have zero thickness and assure just sliding of the oblique front with the detonation rate of this explosive charge. Moreover, since we are interested in the maximal shockwave pressure generated in the substance being loaded (we consider only porous media), we consider the main explosive charge infinitely thick. In this case the influence of gas dispersion from the free surface of the explosive charge on the DP flow pattern cannot be taken into account in the neighborhood of the DP-loaded substance interface. The problem of pressure transmission from the explosive in a compact material through a porous medium was considered in [6] in a similar formulation. The slope of the detonation front to the explosive-powder interface in [6] was arbitrary. The pressure being transmitted in a compact material being hardened by an explosion is estimated in [7] when using two-layer charges when the detonation front slope to the explosive-loaded material interface is also arbitrary. Analysis shows that three flow patterns are possible when porous bodies are loaded by the scheme of Figs. Ib and c, as shown in a coordinate system in Fig. 2 moving together with the oblique detonation front OA at a velocity D. The case when a regular reflection mode holds for the oblique DW and a reflected shock OC exists in the DP repeating the gas flux on the side from the interface is shown in Fig. 2a. Since the flux of the gaseous DP rotated through an angle ~i from the origin is duplicated to the opposite side behind the reflected wave, then the pres